Various method of obtaining a composite composed of silicon carbide and carbon have been proposed. In order to improve the resistance to oxidation and wear, and other properties of carbon material, there have been proposed methods of forming a film of silicon carbide on the surface of a carbon substrate, such as the method of forming a silicon carbide layer on the surface of a substrate by decomposition and reaction of a gaseous silicon compound (e.g., SiO gas), and the method of forming a silicon carbide film on the surface of a substrate by reaction of a gaseous silicon compound (e.g., SiCl.sub.4) and a gaseous carbon compound (e.g., CCl.sub.4 gas). However, the maximum thickness of the silicon carbide layer or film formed by such methods is about 2 mm.
On the other hand, in order to form silicon carbide in a carbon block there have been proposed a method which uses the above-mentioned gas phase reaction, and a method which uses a penetration reaction of molten silicon into a blocked carbon solid. By these methods it is possible to form silicon carbide in the blocked carbon solid to the depth of only several millimeters.
The present inventors once developed a method by which, in order to form silicon carbide deep in a thick carbon block, the carbon block is first oxidized at 400.degree. C.-600.degree. C. to make it porous and light in weight, and then a silicon containing material such as molten metallic silicon is caused to penetrate into and react with the porous block. By this method it is possible to attain a high rate of conversion of carbon to silicon carbide and form a carbon block in which a layer composed of silicon carbide and carbon is formed to the depth of above 1 cm.
Further studies and experiments, however, have disclosed that there are carbon blocks in which the layer composed of silicon carbide and carbon is not formed, but the reaction is limited to the surface thereof.
This invention has been made in view of the above-mentioned problem, and its object is to provide a new composite composed of silicon carbide and carbon and a method of making the same, wherein by selecting the crystallinity and density of a carbon block and simply causing a silicon containing material to penetrate into and react with the carbon block, it is possible to form a thick layer composed of silicon carbide and carbon on the surface of the carbon block with ease and without fail.